Influence of an analog of vasopressin on the reaction of command neurons of defensive behavior of the edible snail during the stimulation of nerves.

An increase was found at the level of the command neurons of defensive behavior in the amplitude of summary excitatory postsynaptic potential (EPSP) recorded in the command neurons in response to nerve stimulation; as were an increase in the probability of the occurrence of an action potential in the reaction, and under certain conditions, a substantial decrease in the rate of habituation during rhythmic (0.1 Hz) nerve stimulation in the presence of a peptide. This last effect was observed when two groups of neurons, the control and those to which the peptide was presented prior to the first stimulation series in the experiment, i.e., without the preceding development of habituation, were compared. The decrease in the rate of habituation affected both the amplitude of the summary EPSP and the probability of the occurrence of an action potential in the reaction. All these changes in the presence of the analog may underlie the increase in spike reactions of the command neurons of defensive behavior, and may thus underlie the initiation or an increase in defensive behavioral reactions. The effects obtained were not long-lived, and took place only in the presence of the peptide in the extracellular milieu.